Accretion onto a black hole in a string cloud background
Abstract
We examine the accretion process onto the black hole with a string cloud background, where the horizon of the black hole has an enlarged radius r_{H}=2M/(1α), due to the string cloud parameter α (0≤α<1). The problem of stationary, spherically symmetric accretion of a polytropic fluid is analyzed to obtain an analytic solution for such a perturbation. Generalized expressions for the accretion rate M˙, critical radius r_{s}, and other flow parameters are found. The accretion rate M˙ is an explicit function of the black hole mass M, as well as the gas boundary conditions and the string cloud parameter α. We also find the gas compression ratios and temperature profiles below the accretion radius and at the event horizon. It is shown that the mass accretion rate, for both the relativistic and the nonrelativistic fluid by a black hole in the string cloud model, increases with increase in α.
 Publication:

Physical Review D
 Pub Date:
 September 2014
 DOI:
 10.1103/PhysRevD.90.064037
 arXiv:
 arXiv:1409.7872
 Bibcode:
 2014PhRvD..90f4037G
 Keywords:

 04.40.Dg;
 95.30.Sf;
 04.50.Gh;
 Relativistic stars: structure stability and oscillations;
 Relativity and gravitation;
 Higherdimensional black holes black strings and related objects;
 General Relativity and Quantum Cosmology
 EPrint:
 9 pages, To appear in Phys. Rev. D